The SuperMac computers are entirely stable and compatible with Mac OS 8.1. As always, it is recommended that one check for updates to the software utilities that came with one's SuperMac computer before upgrading to a new OS version. Some specific test notes are included at the end of this advisory. Also, if you are upgrading to Mac OS 8.1 from Mac OS 7.6.1 or earlier, we strongly recommend that you read the Mac OS 8.0 Technical Report before making the upgrade to 8.1, as certain cautions which apply to Mac OS 8.0 also apply to Mac OS 8.1.

Regarding the new HFS+ Extended Format, there are a number of issues on which we must caution our customers. These issues pertain to any Mac OS computer.

In brief, we recommend that our customers not reformat their drives with the new HFS+ Extended Format unless and until they own a bootable Apple Mac OS 8.1 CD or an HFS+ compatible diagnostics CD, such as Micromat's TechTool Pro or Symantec's Norton Utilities. This is to ensure that users have a means of recovery should anything happen to the OS installation on their hard drive.  Furthermore, J700, J710, S900, and S910 owners with E100 cards in those systems should be advised that the E100 software does not presently format drives in the HFS+ Extended Format. There is a workaround, but owners of these systems are advised not to use the HFS+ Extended Format on drives connected to the E100 card until reviewing the HFS+ info below. When E100 owners are ready to proceed, instructions for creating an HFS+ Extended Format volume with the E100 card can be found in KnowledgeBase record #KB00326.

The HFS+ Extended Format, available under Mac OS 8.1, represents a dramatically different implementation of the Macintosh filing system. Unfortunately, although HFS+ makes more efficient use of drive space, it is incompatible with versions of the Mac OS prior to 8.1. As a result, if you format your hard disk drive to use the HFS+ Extended Format, that drive will only be accessible under Mac OS 8.1 and later. The obvious implication of this are that unless and until you have a bootable Mac OS 8.1 CD (1) you will not be able to access that hard disk drive when booting from your UMAX/SuperMac System CD; (2) you may not be able to easily repair drive-related problems; (3) you will not be able to reinstall Mac OS 8.0 or older versions of the Mac OS without first reformatting the HFS+ drive; (4) you will not be able to reinstall Mac OS 8.1 without reformatting the drive, reinstalling Mac OS 8.0, and then reinstalling Mac OS 8.1 again.

Fortunately, even though one must use at least 8.1 to take advantage of HFS+, one does not need to use HFS+ to take advantage of 8.1. Therefore, the potential pitfalls described above can be avoided simply by installing the Mac OS 8.1 update -- either from an internet download of the 8.1 updater or via the 8.1 CD -- but not reformatting to use the HFS+ Extended Format.

Having the Mac OS 8.1 CD will afford one a means of booting under 8.1, accessing HFS+ boot drives, and, if necessary, reinstalling Mac OS 8.1 on that HFS+ drive. Since reinstalling the system software is an annoying but sometimes necessary maintenance procedure, the importance of having the Mac OS 8.1 CD should be clear. Further, Apple also recommends that one not use an HFS+ Extended Format volume as one's start up disk unless one has the Mac OS 8.1 CD.

The following results encompass Mac OS 8.1 compatibility with the software packages bundled with SuperMac computers. Software not bundled by Umax is beyond the scope of this report. Test systems were the C600x/280 (w/CacheDoubler) and S900 (multiple models & configurations).

TechTool Pro 1.0.5u
SYMPTOM: File Tests are greyed out.
CAUSE: "System" and "Finder" files are new and not recognized by this version of TechTool Pro. SOLUTION: Download the TechTool Pro 1.0.6u update.

NetDoubler
SYMPTOM: If NetDoubler Client is active, the copy may stop due to a "disk error".
CAUSE: This appears to be the case whether connected to another NetDoubler-equipped computer or not.
SOLUTION: Using the "disable" radio button in the NetDoubler control panel will allow the copy, though disabling the whole package may be preferrable.

Norton Disk Doctor 3.5.1
SYMPTOM: Running this on an extended format volume under Mac OS 8.1 may yield errors with the Master Directory Block (MDB) and the Alternate MDB. Most commonly, these are 3,2,14 and 3,3,14. Asking Disk Doctor to fix these will result in losing the hard drive -- Disk First Aid will not be able to repair it.
CAUSE: Norton Disk Doctor 3.5.1 does not support HFS+.
SOLUTION: Norton Disk Doctor 3.5.2 addresses the issue by disabling repairs on HFS+ volumes (so as not to actually damage them). Later updates will directly support HFS+.

CD-ROM Toolkit 2.3.2
SYMPTOM: After installing, one may see a dialog which reports a corrupted cache file and directs the user to delete it.
CAUSE: This dialog may appear only on C500 and C600 models, possibly because the CD (SCSI) and HD (IDE) are on different buses.
SOLUTION: If one dismisses this dialog, everything appears to function normally.

Apple Multiprocessor HAL
SYMPTOM: Frequent and apparently inexplicable crashes in processor-intensive applications such as Adobe Photoshop.
CAUSE: This extension may be incompatible with Mac OS 8.1.
SOLUTION: This extension should be removed from the Multiprocessing folder within the Extensions folder on SuperMac S900DP multiprocessing systems.

The following have undergone cursory testing and did not exhibit any change in behavior:

• ClarisWorks 5.0
• Claris Organizer 2.0
• Acrobat Reader 3.0.1
• Motorola Math Library ("LibMotoSh" extension)
• Matrox acceleration
• EarSaver
• Newer Technology's Gauge Series Utilities
• Global Village Teleport SpeakerPhone Edition (please see KnowledgeBase record #KB00333 for information regarding the SuperMac C600's internal modem).

The following have not been tested:

• Now Contact/Up-to-Date -- no longer bundled, no longer being developed; will not be tested.
• Now Utilities -- known incompatible w/Mac OS 8.0; no longer bundled, no longer being developed; will not be tested.
• Conflict Catcher -- known incompatible w/HFS+, may be disabled on some systems; will not be tested.
• MegaPhone 2.0.7 -- UMAX-bundled version (and all other releases prior to 2.1) incompatible with Mac OS 8.1; will not be tested.
• PowerFPU